Mysql有效索引(Mysql effective indexes)

 我的队友，我刚刚在一个VPC中实现了ELB，在不同的可用区域中有2个私有子网。 您得到超时的原因是，对于添加到负载平衡器的每个子网，它将获得一个外部IP地址。 （尝试'dig elb-dns-name-here'，你会看到几个IP地址）。 如果其中一个IP地址映射到一个私有子网，它将超时。 映射到公共子网中的IP地址将会起作用。 因为DNS可能会给你任何一个IP地址，有时它的工作，有时它超时。 
 
 经过一些亚马逊回来之后，我们发现ELB应该被放置在“公共”子网中，即有一条路由到Internet Gateway的子网。 我们希望将我们的网络服务器保留在我们的私有子网中，但允许ELB与他们交谈。 为了解决这个问题，我们必须确保我们在每个可用区域中都有一个相应的公共子网，我们有私有子网。 然后，我们将ELB添加到每个可用区域的公共子网。 
 
 起初，这似乎没有起作用，但是在尝试了一切之后，我们重新创建了ELB，并且一切正常工作。 我认为这是一个错误，或者ELB从这么多变化中处于一个奇怪的状态。 
 
 这里或多或少是我们所做的： 
 
 
 
 WebServer-1在可用区域us-east-1b中的PrivateSubnet-1中运行，安全组称为Web服务器。 
 
 
 WebServer-2在可用区域us-east-1c中的PrivateSubnet-2中运行，安全组称为Web服务器。 
 
 
 在区域us-east-1b中创建一个公共子网，我们称之为PublicSubnet-1。 我们确保将包含到Internet Gateway（ig-xxxxx）的路由的路由表与此新子网相关联。 （如果您使用向导创建公用/私有VPC，则此路由已存在。） 
 
 
 在区域us-east-1c中创建一个公共子网，我们称之为PublicSubnet-2。 我们确保将包含到Internet Gateway（ig-xxxxx）的路由的路由表与此新子网相关联。 （如果您使用向导创建公用/私有VPC，则此路由已存在。） 
 
 
 创建一个新的ELB，添加到PublicSubnet-1和PublicSubnet-2（而不是PrivateSubnet-X）。 此外，选择在ELB中运行的实例，在这种情况下是WebServer-1和WebServer-2。 确保分配一个允许传入端口80和443的安全组。让我们调用此组elb-group。 
 
 
 在Web服务器组中，允许来自elb组的端口80和443的流量。 
 
 
 我希望有帮助！ 

My teammate and I just have implemented ELB in a VPC with 2 private subnets in different availability zones. The reason you get timeouts is that for each subnet you add to the load balancer, it gets one external IP address. (try 'dig elb-dns-name-here' and you will see several IP addresses). If one of these IP address maps a private subnet, it will timeout. The IP that maps into your public subnet will work. Because DNS may give you any one of the IP addresses, sometimes it works, sometimes it times out. 
 
After some back and forth with amazon, we discovered that the ELB should only be placed in 'public' subnets, that is subnets that have a route out to the Internet Gateway. We wanted to keep our web servers in our private subnets but allow the ELB to talk to them. To solve this, we had to ensure that we had a corresponding public subnet for each availability zone in which we had private subnets. We then added to the ELB, the public subnets for each availability zone. 
 
At first, this didn't seem to work, but after trying everything, we recreated the ELB and everything worked as it should. I think this is a bug, or the ELB was just in an odd state from so many changes. 
 
Here is more or less what we did:
 
 
 
WebServer-1 is running in PrivateSubnet-1 in availability zone us-east-1b with security group called web-server. 
 
 
WebServer-2 is running in PrivateSubnet-2 in availability zone us-east-1c with security group called web-server. 
 
 
Created a public subnet in zone us-east-1b, we'll call it PublicSubnet-1. We ensured that we associated the routing table that includes the route to the Internet Gateway (ig-xxxxx) with this new subnet. (If you used the wizard to create a public/private VPC, this route already exists.) 
 
 
Created a public subnet in zone us-east-1c, we'll call it PublicSubnet-2. We ensured that we associated the routing table that includes the route to the Internet Gateway (ig-xxxxx) with this new subnet. (If you used the wizard to create a public/private VPC, this route already exists.) 
 
 
Created a new ELB, adding to it PublicSubnet-1 and PublicSubnet-2 (not the PrivateSubnet-X). Also, picked the instances to run in the ELB, in this case WebServer-1 and WebServer-2. Made sure to assign a security group that allows incoming port 80 and 443. Lets call this group elb-group. 
 
 
In the web-server group, allow traffic from port 80 and 443 from the elb-group. 
 
 
I hope that helps!